Protego Bets on a New Path for Amyloidosis With $130M Raise

San Diego–based Protego Biopharma has raised $130 million in Series B funding to advance a new therapeutic approach for AL amyloidosis , a rare and often fatal disease caused by misfolded antibody fragments known as light chains. The company’s lead drug, PROT-001 , is designed to stabilize these proteins before they misfold and accumulate — a shift from the traditional strategy of treating the damage after it occurs. Early clinical data is expected next year, with a Phase 2/3 trial planned for the second half of 2026.

The timing is significant. Several competitors have stumbled recently: both ProthenaDealroom has a profile for this one. Try Dealroom → and AstraZenecaDealroom has a profile for this one. Try Dealroom → saw their amyloidosis programs fall short in clinical testing this year, despite years of investment. Those failures targeted the removal of existing toxic deposits. Protego is betting that intervening earlier — before the proteins clump together — may offer a more direct way to slow or halt the disease’s progression. CEO Brent WarnerDealroom has a profile for this one. Try Dealroom → argues that growing scientific evidence points to these unstable light chains as the core driver of organ damage and mortality.

Protego’s strategy draws from the work of Jeffery Kelly , a Scripps Research scientist and co-founder of the company. Kelly previously helped develop Vyndamax , the first U.S.-approved stabilizer for transthyretin amyloidosis, now a blockbuster drug under Pfizer. That precedent matters: it demonstrated both the scientific and commercial potential of protein-stabilizing therapies, and it laid the foundation for Protego’s belief that misfolding can be intercepted rather than merely managed.

If PROT-001 can validate that approach, it could complement — and potentially improve — existing treatments like Darzalex and chemotherapy, which aim to eliminate the plasma cells producing the misfolded proteins. Patients often relapse because some of those cells eventually return. Adding a stabilizer, Warner says, could lead to “faster, deeper, and more durable responses.” In his words: “You don’t always need a sledgehammer — sometimes a sharper knife will do.”

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